Breakign down EFI options

[bobcowan]

I'v been messing with performance EFI for a few years now. I wouldn't say I'm an expert, but I have done my home work. The learning curve can be steep. But I'll probably never go back to a carb.

Self tuning a myth and a marketing buzz word. Doesn't happen. The computer can get itself to about 75% or so of where you need to be. But you'll need to understand how it works so you can get it where it needs to be. Especially on a performance engine. Some dyno time with a pro can dial it in to run like a stocker.

I think throttle body EFI is not worth the expense and effort. Because it's a wet manifold, you end up with some of the same charectoristics of a carb system. Port injection (like stock engines) work really, parts are inexpensive, and are dead on reliable. Stack system look great, perform really well, but do require some extra work to get them running right. Stack systems are not a simple bolt on and go.

EFI will "tame" a big cam. The problem with a big cam and a carb is that you tend to lose intake charge velocity at lower rpm's. Because the air/fuel mixture is moving at such a slow speed, the fuel falls out of suspension and puddles in the intake; same thing with a throttle body. That's why engines with big ports and carbs idle at such high speeds. Port injection makes a significant improvement in that area. A big cam with big ports will idle like a ***** cat at 800 rpm's, and drive around town without a hiccup.

Cam shaft selection can make a big difference, depending on the EFI system you use. A throttle body will run fine on pretty much any cam that you choose. Port injection will do better with a cam designed for EFI, but can still be fine with the average hydraulic roller cam. An individual runner system really needs a cam with a wide LSA, like 114*. A big cam with narrow LSA will create a lot of reversion, and create that "cloud" effect that Webers were famous for.

Most EFI components are pretty standard, and not a lot of difference between one system and another. The ECU is, of course, the heart of the system. It takes in information, makes decisions, and then acts on them. The more complicated the system is, the better decisions it makes. And the harder it is to tune. It's a trade off. A carb is extremly easy to tune, but it's not very accurate.

Many ECU's have a lot of features to do a lot of stuff. Fuel, spark, turbo, traction control, multiple fuels, cam timing, etc. Don't waste money on features you'll never use.

I like the ability to use E-85. On a hot day or on the track, E-85 really runs well, makes excellent power, and keeps the engine cool. I have a switch under the dash to go back and forth between the two fuels. My ECU can use a factory fuel sensor, but for a variety of reasons I chose not to use it.

Modern engines use some kind of meter to measure incoming air, and O2 sensors in the exhaust to measure outgoing exhaust. It measures those qualities, and then makes decisions on the amount of fuel to be injected and timing to use. That's referred to as "closed loop". These are the most accurate, and if your engine isn't too radical, you should try to use that.